Dynamics of cogeneration plants; Combined cycles

The increasing demand for economic procedures due to the limited natural resources as well as greater efforts for environmental protection, led to a reorientation in power plant engineering. Main interest is still the improvement of thermal efficiency, since it means a lower specific fuel consumption on the one hand, and a reduction of pollutant emission on the other. However, a further increase of steam parameters offers limited means for improving thermal efficiency of steam power stations. Excessive price of highly alloyed materials and the sensibility to temperature changes are prohibitive. Another feasible way is cogeneration based on a dual steam gas process, even for the aspect of specific capital costs. This paper focuses on how, beyond the thermodynamical design for high plant efficiency, combined cycle units have to fulfill the requirements of flexibility in operation.